Provided are a method, system, and computer-readable medium for determining whether a copy number variation exists in a sample genome. The method includes sequencing a sample genome to obtain a sequencing result formed by multiple reads; comparing the sequencing result with a reference genome sequence to determine the distribution of the reads on the reference genome sequence; determining, based on the distribution of the reads on the reference genome sequence, multiple breakpoints on the reference genome sequence, wherein the number of the reads on either side of each breakpoint are significantly different; determining, based on the plurality of breakpoints, a detection window on the reference genome; determining, based on the reads falling in the detection window, a parameter; and determining, based on the difference between the first parameter and a preset threshold, whether a copy number variation exists in the sample genome against the detection window.